1. The area of windows needed for light and ventilation depends on the size of rooms, and rooms are generally smaller on upper stories of the building—the communal rooms are generally on the ground floor and more private rooms upstairs.
2. The amount of daylight coming through a window depends on the area of open sky visible through the window. The higher the window, the more open sky is visible (because nearby trees and buildings obscure less)—so less window area is needed to get sufficient daylight in.
3. To feel safe on tile upper stories of a building, one wants more enclosure, smaller windows, higher sills—and the higher off the ground one is, the more one needs these psychological protections.
Therefore:
On no account use standard doors or windows. Make each window a different size, according to its place.
Do not fix the exact position or size of the door and win-
221 NATURAL DOORS AND WINDOWS
dow frames until the rough framing of the room has actually been built, and you can really stand inside the room and judge, by eye, exactly where you want to put them, and how big you want them. When you decide, mark the openings with strings.
Make the windows smaller and smaller, as you go higher in the building.
** ,
, _ variation in window size
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the position of the doors and windows “felt”
Fine tune the exact position of each edge, and mullion, and sill, according to your comfort in the room, and the view that the window looks onto—low sill (222), deep reveals (223). As a result, each window will have a different size and shape, according to its position in the building. This means that it is obviously impossible to use standard windows and even impossible to make each window a simple multiple of standard panes. But it will still be possible to glaze each window, since the procedure for building the panes makes them divisions of the whole, instead of making up the whole as a multiple of standard panes—small panes (239). . . .
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| 222 LOW SILL |
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. . . this pattern helps to complete natural doors and windows (221), and the special love for the view, and for the earth outside, which zen view (134), window place (180) and windows overlooking life (192) all need.
One of a window’s most important functions is to put you in touch with the outdoors. If the sill is too high, it cuts you off.
The “right” height for a ground floor window sill is astonishingly low. Our experiments show that sills which are 13 or 14 inches from the floor are perfect. This is much lower than the window sills which people most often build: a standard window sill is about 24 to 36 inches from the ground. And it is higher than French doors and windows which usually have a bottom rail of 8 to 10 inches. The best height, then, happens to be a rather uncommon one.
We first give the detailed explanation for this phenomenon, and we then explain the modifications which are necessary on upper floors.
People are drawn to windows because of the light and the view outside—they are natural places to sit by when reading, talking, sewing, and so on, yet most windows have sill heights of 30 inches or so, so that when you sit down by them you cannot see the ground right near the window. This is unusually frustrating—you almost have to stand up to get a complete view.
In “The Function of Windows: A Reappraisal” (Building Science, Vol. 2, Pergamon Press, 1967, pp. 97-121), Thomas Markus shows that the primary function of windows is not to provide light but to provide a link to the outside and, furthermore, that this link is most meaningful when it contains a view of the ground and the horizon. Windows with high sills cut out the view of the ground.
On the other hand, glass all the way down to the floor is undesirable. It is disturbing because it seems contradictory and
105 1
even dangerous. It feels more like a door than a window; yon have the feeling that you ought to be able to walk through it. If the sill is 12 to 14 inches high, you can comfortably see the ground, even if you are a foot or two away from the window, and it still feels like a window rather than a door.
On upper stories the sill height needs to be slightly higher. The sill still needs to be low to see the ground, but it is unsafe if it is too low. A sill height of about 20 inches allows yon to see most of the ground, from a chair nearby, and still feel safe.
Therefore:
When determining exact location of windows also decide which windows should have low sills. On the first floor, make the sills of windows which you plan to sit by between 12 and 14 inches high. On the upper stories, make them higher, around 20 inches.
Make the sill part of the frame, and make it wide enough to put things on—waist-high shelf (201), frames as thickened edges (225), windows which open wide (236). Make the window open outward, so that you can use the sill as a shelf, and so that you can lean out and tend the flowers. If you can, put flowers right outside the window, on the ground or raised a little, too, so that you can always see the flowers from inside the room—raised flowers (245). . . .
| 223 DEEP REVEALS |
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. . . this pattern helps to complete the work of light on two sides of every room (15 9), by going even further to reduce glare; and it helps to shape the frames as thickened edges (225).
Windows with a sharp edge where the frame meets the wall create harsh, blinding glare, and make the rooms they serve uncomfortable.
They have the same effect as the bright headlights of an oncoming car: the glare prevents you from seeing anything else on the road because your eye cannot simultaneously adapt to the bright headlights and to the darkness of the roadway. Just so, a window is always much brighter than an interior wall; and the walls tend to be darkest next to the window’s edge. The difference in brightness between the bright window and the dark wall around it also causes glare.
Glare . . . and no glare.
To solve this problem, the edge of the window must be splayed, by making a reveal between the window and the wall. The splayed reveal then creates a transition area—a zone of intermediate brightness—between the brightness of the window and the darkness of the wall. If the reveal is deep enough and the angle just right, the glare will vanish altogether.
But the reveal must be quite deep, and the angle of the splay quite marked. In empirical studies of glare, Hopkinson and
Petherbridge have found: (i) that the larger the reveal is, the less glare there is; (2) the reveal functions best, when its brightness is just halfway between the brightness of the window and the brightness of the wall. (“Discomfort Glare and the Lighting of Buildings,” Transactions of the Illuminating Engineering Society, Vol. XV, No. 2, 1950, pp. 58—59.)
Our own experiments show that this happens most nearly, when the reveal lies at between 50 and 60 degrees to the plane of the window; though, of course, the angle will vary with local conditions. And, to satisfy the need for a “large” reveal, we have found that the reveal itself must be a good 10 to 12 inches wide.